PowerShell/src/System.Management.Automation/engine/AutomationNull.cs

/********************************************************************++
Copyright (c) Microsoft Corporation.  All rights reserved.
--********************************************************************/
using System;
using System.Management.Automation;

namespace System.Management.Automation.Internal
{
    /// <summary>
    /// This is a singleton object that is used to indicate a void return result.
    /// </summary>
    /// <remarks>
    /// It's a singleton class. Sealed to prevent subclassing. Any operation that
    /// returns no actual value should return this object AutomationNull.Value.
    /// Anything that evaluates an MSH expression should be prepared to deal
    /// with receiving this result and discarding it. When received in an
    /// evaluation where a value is required, it should be replaced with null.
    /// </remarks>
    public static class AutomationNull
    {
        #region private_members

        // Private member for Value.
        private static readonly PSObject value1 = new PSObject();

        #endregion private_members

        #region public_property

        /// <summary>
        /// Returns the singleton instance of this object.
        /// </summary>
        public static PSObject Value
        {
            get
            {
                return value1;
            }
            // no setter. It is a readonly; So, Value can not be modified. (Immutable).
        }

        #endregion public_property
    }
} // namespace System.Management.Automation